Collapsible steering column assemblies are known in the art for including in vehicles to reduce the likelihood of injury to occupants of the vehicles during collisions. The steering column assemblies include a support for attachment to the vehicle. A steering column is movably supported by the support. An energy absorbing mechanism interconnects the steering column and the support for absorbing energy in response to the steering column moving relative to the support, i.e., when a force is exerted on the steering column such as during the collision.
Common energy absorbing mechanisms include a metal strap that is wrapped about an anvil. The metal strap is generally fixed to the steering column and the anvil is fixed to the support. During the collisions, when the force is exerted on the steering column, the metal strap is forced about the anvil. The metal strap resists the movement and bends about the anvil, thus absorbing the energy and allowing the steering column to move in relation to the support. One of the problems with the energy absorbing mechanisms is that the metal straps are selected to deform when a force exerted on the steering column exceeds a predetermined threshold. As a result, the energy absorbing mechanism is exhausted after absorbing the energy when the force exceeds the threshold and cannot absorb additional energy thereafter. For example, during the collision, the force of the collision itself may exceed the predetermined threshold. In the event that the occupant impacts the steering column shortly thereafter, the energy absorbing mechanism cannot absorb any more energy. Furthermore, collisions generate forces of various magnitude on the steering column, depending on the speed of the vehicles involved, among other variables. The metal straps, chosen to deform at the predetermined threshold, are not suitable to absorb energy at forces below or substantially above the predetermined threshold. In other words, the metal straps, because of the predetermined threshold, are based on predetermined collision conditions and cannot adjust to actual collision conditions. In addition, the metal straps, once deformed, lose structural integrity and must be replaced.
Thus, there is an opportunity to provide an energy absorbing mechanism that is capable of adjustment to absorb energy at forces of various magnitude such that a universal energy absorbing device may be installed on each type of vehicle and adjusted based on individual parameters of the vehicle.